December 7, 2012

One question that several of you have asked pertains to designing an in-wall speaker: how does it differ from designing a regular speaker? What factors do you have to take into account when you’re engineering it?

I caught up with Andrew Welker in our anechoic chamber (this time we put the floor in so I could turn the camera around!) and asked him about his strategy.

Andrew: The biggest challenge with an in-wall speaker is the fact that you are mounting it in a wall, which is not an ideal place for a speaker. The challenge involved in designing an in-wall speaker for that application is firstly most homes in North America are built with standard 2×4 studded walls, so you’ve got a very shallow opening that you have available to mount the speakers in.

The problem with that is that, all else being equal, the more cabinet volume you have available or the more space you have inside the speaker, the more bass that you can get out of it, particularly at the lower frequencies. So you’re limited in the amount of space that you can actually use up because of that standard 2×4 studding.

As an example here, we’ve got two speakers that are essentially identical models. One is the T2 In-Wall Speaker, the other is our M2 Bookshelf Speaker, and if I turn them sideways you can see the T2 in-wall is a tiny tiny little cabinet. It’s probably got less than 1/3 of the internal cabinet volume of the M2. So that would lead you to believe that an in-wall speaker such as this would have no bass.

The benefit of having the wall is that the wall boundary itself that’s going to surround all the sides of the speaker helps to increase the amount of bass you get from the speaker. It’s called the boundary loading effect. As long as we design the in-wall speaker in that boundary, we can now get a smooth balance and we can get good low-frequency response.

We’re standing inside our anechoic chamber, and in here we actually use a false all which we mount the in-wall speaker into so that we can get an idea of what the typical boundary loading is going to be. Now, you’re still not going to get as much bass out of an in-wall as you would out of the equivalent bookshelf model. But when you blend that system with a subwoofer, it’s going to give you performance that is pretty much identical to what you would get with a pair of a bookshelf speakers with that subwoofer.

So that’s really the biggest challenge: that we don’t have a lot of mounting space available when designing an in-wall product.